Handle control system



Jan. 14, 1947. H, HULL ET Al.

I HANDLE CONTROL SYSTEM Filed July 23, 1941 4 Sheets-Sheet l F n E; 55 C HH/VDL E reaA/SM/rrffs f/oro@ F i ET Jan. 14, 1947.

H. L. HULL ET AL HANDLE CONTROL SYSTEM Filed July 23, 1941 F' I E-Y 4 Sheets-Sheet 2 IZOI ,2g

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PREDICTION POTENTIOME TIME OF gg IIB" TER

AMPLn-ms RATE `H7 |09 AMPLlFlER //-m (t OTHER \l l5 PREDICTION H3 voLTAGEs INVENTURS HARVARD L. HULL WILLIAM C. HARTMAN RAYMOND C. GOERTZ aww/M T EIR ATTOR EY Jam 14, 1947' H. HULL ETAL 2,414,102

HANDLE CONTROL- SYSTEM Filed July 2s, 1941 4 sheets-sheet s A.c.AMP| |F|ER AND PHASE s IF ER MODULATOR DC 1, AMPLIFIE -f [5.c.AMFLlFlL-RoJ 59 MoDuLAToR WAVE o AND A.c.AMpl |F|ER MoDULATo n n o l 16| INVENToRs HARVARD L. HULL WILLIAM C. HARTMAN RAYMOND C. GOERTZ 7mm/.M

THE! R ATTORNEY Jan. 14, 1947.

H. L. HULL Erm. 2,414,102 HANDLE CQNTROL SYSTEM Filed July 23, 1941 4 sheets-sheet 4' D.c.ouTPuT V277 V- mveNroRs HARVARD L.HuLL

WILLIAM C. HARTMAN RAYMOND c. GpeRTz THE l R ATTORNEY atented Jan. 14, 1947 HANDLE CONTROL SYSTEM Harvard L. Hull, Garden City, William C. Hartman, Bohemia, and Raymond C. Goertz, Hempstead, N. Y., assignors to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application July 23,

23 Claims. E

The present invention relates, generally, to re control apparatus, and has reference, more particularly, to sights for gun directors, in which a telescope sight is continuously trained on a target, thereby enabling the production and transmitting of data to cause a gun to be aimed at the target.

In previous devices of this type, control has been obtained by means of a handwheel, whose motion had to be synchronized with motion of the telescope. Also, separate controls for azimuth and elevation were used. These devices were quite satisfactory for low tracking rates. However, with high tracking rates, such as are necessary in close-in aerial combat, proper synchronization of controls and telescope becomes diftlcult and it is not possible to obtain satisfactory control so as to be able to readily and rapidly manipulate the controls to cause the telescope to track with the course of fast moving targets, and still be steady and precise in operation so that a target once sighted may be continuously followed with ease and accuracy and smooth rates obtained for prediction purposes.

The present invention provides a device which minimizes the difiiculties of prior devices. A tracking control system is provided in which the velocity of the sight is controlled by natural and instinctive movements of a `single control handle controlling both azimuth and elevation movement of the sight, and whose operation simulates direct manual control of the sight. Precision and steadiness of operation are provided in the type of control unit used, in which the operator can rmly grasp a reference knob, which is fixed with respect to the sight, with part of his hand and the control handle with the rest of the same hand. This provides a steadying influence on the control process, so that extremely ne control is possible. The control handle is made fairly stili in operation, by a cantilever type mounting, making control mainly by pressure rather than by deiiection. In addition, the present system permits complete control with one hand, leaving the operators other hand free for other duty.

A further feature of the device resides in a switching arrangement whereby the velocity con- ,trol may be converted to a combined velocity and acceleration control which, under some circumstances, will give constant velocity tracking Without any action by the operator, whereby tracking on a target is maintained automatically at a fixed speed. Also, means are provided for compensating the data obtained from the tracking sight for any desired prediction data, and for transmittingthe compensated data to a remote point to control the directing of a gun.

Accordingly, it is an object of the present invention to provide a new and improved tracking control system for sights and gun directors.

1941, Serial No. 403,618

(ci. :is-49) It is also an object o the invention to provide an improved control unit for precise and steady tracking control.

It is a further object to provide an improved control circuit for controlling the tracking velocity of a sight in both azimuth and elevation by manipulation of a single control handle.

It is an additional object to provide improved means for effecting velocity control or combined velocity and acceleration control of a. tracking system, at the will oi the operator.

It is another object to provide an improved circuit and mechanism for compensating the gundirecting data obtained by the tracking system for any desired prediction data.

It is still a further object to provide an improved modulator circuit for converting direct voltages into alternating voltages whose phase and magnitude correspond to the polarity and magnitude of the direct voltages, for use in tracking control.

It is an additional object to provide an improved demodulator circuit for converting alternating voltages into direct voltages whose polarity 25 and magnitude correspond to the phase and magnitude of the alternating voltages, for use in tracking control.

Other objects and advantages of this invention will become apparent as the description proceeds.

In the drawings,

Fig. l shows in schematic perspective view the mechanical arrangement of the tracking and prediction control;

Fig. 2 shows a longitudinal cross-section of the signal pick-up or control unit used in the device of Fig. 1;

Fig. 3 shows schematically the circuit diagram of an alternating-current-operated control circuit for the device of Fig. 1;

Fig. 4 shows schematically an alternative direct-current-operated control circuit for the device of Fig. 1, including acceleration control;

Fig. 5 shows a detailed circuit of a push-pull 45 modulator circuit suitable for use with the circuit f Fig. 4; and

Fig. 6 shows the detailed circuit of a full-wave phase-sensitive demodulator suitable for use with the circuit of Fig. 4. 60 Similar characters of reference are used in all of the above figures to indicate corresponding parts.

Fig. 1 shows the mechanical arrangement of the various elements of the system. The tele- 55 scope tracking sight I is mounted for rotation in azimuth, as by means of vertical shaft 3, and is pivoted about a horizontal axis 2 for rotation in elevation. Horizontal shaft is rotatably mounted on shaft 3 as by a, yoke 4 and is positioned t0 parallel to the horizontal axis 2 of sight l. Shaft is linked to sight I as by a linkage 1, 8. so that sight I is rnoved in elevation in synchronism with s rotation of shaft 5. Control unit 9, shown in detail in Fig. 2, is fixed to shaft 5 with its control handle II parallel to sight I. Hence, the control unit 9 is relatively fixed with respect to sight I and always remains parallel to sight I, turning with sight I both in elevation and azimuth. This gives the operator the sense of actually manually operating the sight I, by manipulation of control handle II, since the sight appears to respond to his natural movements in effecting tracking, although actually the control handle II merely controls the sight driving mechanism, as described below.

The control handle II and its related parts are so shaped and formed as to provide easy and natural manipulation by the operator. For this purpose, referring to Fig. 2, casing 55 has fastened to it a stabilizing or reference knob 50, placed concentric and adjacent to handle- I I. Knob 5I) is shaped to be gripped by the thumb and fore part of the hand of the operator. This knob 50 is relatively short in length, so that the rear or heel portion of the hand of the operator will at the same time be able to grip the handle II. The control circuit described below is designed to give full speed control for a relatively small displacement of control handle Il, which may be on the order of 1/8 inch for full displacement. Accordingly, by this deviceLthe operator is given a fixed reference object by which to gage the pressure (or deflection) to be placed on the control handle, while maintaining a. firm grasp and positive control of the control handle. The effect is to enable extremely accurate and steady control with a minimum of operator effort. The complete operation is made natural, enabling instinctive reaction to changing conditions needing control adjustment on the part of the operator.

Referring again to Fig. 1, also fastened to horizontal shaft 5 is a gear I3 driven by driving gear I5 which in turn is driven by drive motor I1. Speed generator I9, whose function is described below, is also driven directly by drive motor I1. The drive motor I1 thereby rotates shaft 5, and controls the elevation of sight I at a speed which may be proportional to the deflection of, or pressure on, control handle II, as will be described below. Strict proportionality need not be followed in all cases. For example, it may be desirable to give relatively broad and insensitive control near the neutral axis of the control unit, and relatively sharp and sensitive control at larger velocities.

Also connected lto shaft 5 is a differential 2I connected in turn to further shafts 23 and 25. Shaft 25 is positioned by prediction motor 21 which also drives prediction potentiometer 29. Shaft 23 drives a coarse self-synchonous transmitter 3| directly, and a fine self-synchronous transmitter 33 through suitable gearing 35. The outputs of these transmitters 3| and 33 may go to control the elevation of a remotely situated gun (not shown) ,which will then be directed (at least in elevation) toward the target being sighted by telescope I. Prediction motor 21 and dierential 2|, cause the shaft 23 to lead or lag the shaft 5 by an angle corresponding to any corrections necessary to cause the gun to be directed toward the future position of the target. Such corrections may allow for time of night of the projectile, super-elevation, wind, air density, etc.

Shaft 3 is driven in azimuth by exactly the same type of system, through a coupling gear 31'. thereby giving complete control of the sight and/or gun in elevation and azimuth. Similar elements are given the same reference numbers, but primed.

Fig. 2 shows a cross-section of the control unit 9. 'Ihis control unit 9 has four symmetric magnetic circuits disposed radially about the longitudinal axis 42 of the unit, only two such circuits being shown in the cross-section taken. 'I'hese circuits have a common portion 4I formed as a sleeve concentric with axis 42. Extending radlally from sleeve 4I are four core members, only two of whlchv(43, 45) are shown. These core members 43, 45 have bent over arms or portions 41, 49 parallel to axis 42. These arms are terminated by slanted portions. which are preferably formed to comprise a portion of the surface of a sphere having its center approximately at point C. The magnetic circuits are completed by a button 5I having a spherical surface which cooperates with the spherical-shaped ends 48 of arms 41, 49 to form a uniform air gap between button 5I and each of the arms-41, 49. It is to be understood that each of the two arms not shown is formed in exactly the same manner, but disposed in a plane perpendicular to the plane of the figure.

Button 5I is rigidly fastened to handle II as by rod 53, and is resiliently fastened to case 55 by member 51 whose end 6I is rigidly held to case 55, as by set screws 63, and which has a reduced resilient bending section 59. The handle and button assembly is adjusted so as to be normally coaxial with axis 42, but may be deiiected in any radial direction by a transverse pressure on handle II. The button 5I is thus mounted in cantilever fashion, all bending taking place approximately at the center C of the reduced diameter bending section 59. The motion of button 5I approximately follows the surface of a sphere having its center at point C, which is at the center of bending section 59. Because of this cantilever action, the deflection of the control handle I I is closely proportional to the pressure applied to it. Since the tracking velocity of sight I may also be proportional to the deflection of handle II, it will, in such case, be proportional to applied pressure. Hence, the operator gets a realistic feel of the operation, and can readily imagine that his own effort is controlling the sight directly. This makes it easier for the operator to accurately perform the required tracking.

Placed about sleeve 4I is an energizing coi-l 65, which is fed from a suitable source of alter-v nating current. Around each arm, as for example arms 41, 49, there is wound a pick-up coil. Two such coils 61, 59 are shown. The entire device is made symmetrical about axis 42, so that equal voltages of equal phase will be induced in each pick-up coil when button 5I is coaxial with axis 42. Each pair of diametrically opposite coils is connected in series in opposing rela non, so that, when button 5| is in its undenected position, coaxial with axis 42, thereby making all four magnetic circuits identical, no resultant voltage is produced from each pair of pick-up coils, since the voltage induced in any one coil is opposed and cancelled by that of its diametrically opposite coil.

When handle II is deflected, for example, vertically downward, the air gaps between button 5I and arms 41, 49 will remain of the same length, since button 5I will pivot about its approximate center of curvature C; however, the cross-sectional varea of the gap at arm 41 will decrease, increasing the reluctance of its magnetic circuit, and the area. at arm t9 will increase, reducing the reluctance of its circuit. more voltage will be induced in coil 69 than in coil B1, and there will be a net voltage output, indicating deflection along the vertical direction'. No voltagewill appear across the other pair of coils. in this instance, however, since their magnetic circuits remain balanced. For deflection upward, the opposite will occur, and the output voltage will be of opposite phase from that of the case first considered. For any other direction of deflection a component of voltage will appear across each pair of coils which will be proportional in magnitude to the component of deflection along the axis of that pair of coils, and will have a phase corresponding to the sense of the corresponding component of deflection. The unit is mounted so that one pair of coils has a vertical axis perpendicular to shaft 2 and the other a horizontal axis perpendicular to shaft 3. Then the control signal output of the vertical pair of coils is used to control the elevation of the sight I and the output of the horizontal pair is used to control azimuth. as will be described below.

Fig. 3 shows the circuit diagram for alternating current control in one plane, either in azimuth or elevation, the same circuit being duplicated for the other plane'. The energizing coil 65 of control unit 9 is energized from a source 13 of alternating current by means of a currentlimiting resistor 15 which minimizes saturation eiects. The two oppositely positioned pick-up coils t1, 09 are connected in series opposition and are shunted by a condenser 11 whose function is to bypass the harmonics created by saturation of the edges of button 5I. This condenser l1 may tune the output coils 61, 69 to resonance at line frequency. The voltage output from control unit 9 is then an alternating voltage of supply line frequency having an amplitude proportional to the deflection of control handle II (in elevation or azimuth) and a phase corresponding to the sense of the deflection. This control voltage is applied over coupling transformer 19 and conventional phase shifter 8| to amplifier 83, which amplifies the control voltage and applies it to one winding 85 of the two phase drive motor I1, the other winding 81 being connected directly 4 to the supply line 13. Phase shifter 8| assures that the voltage `applied to winding 85 is in quadrature with that applied to Winding 81. Since the control voltage will reverse phase upon i reversal of the control handle displacement, it will be seen that the direction of rotation of L. drive motor I1 will also reverse, and will accorda `lngly .correspond at all times to the direction of deflection of the control handle Il.

1 tion.`

In order to assure that the speed of rotation of drive motor I1 will be proportional to the deflection of control handle II, when this condition is desired, speed generator I9 is directly driven by drive motor I1. This speed generator is designed to have an alternating voltage output directly proportional toits speed. In one illustrative embodiment this generator may take the form of a Barber-Colman #412 reversible alternating current motor. This motor has an energizing winding 89 and a two-phase winding 9| 93, all iixed. The rotor 95 is of the squirrel cage 'type It has been discovered that such a motor,

Hence j The direcwhen its winding 99 is energized and its rotor is turned, will generate voltages in its two-phase winding which, when added, will be closely proportional to the speed of rotation. Alternatively, 5 this generator may take the form shown in Riggs Patent 2,206,920, issued July 9, 1940. Winding 89 Iis energized from supply line 13 through an adjustable phase shifting circuit 91. The windings 9I 93 are connected in series across a. potentiometer 99 whose movable tap I0| is connected to the junction of the two-phase windings 9|, 93. This tap I 0| is adjusted so that at standstill there is zero voltage output. A condenser |00 is connected across windings 9|, 93 to iilter l5 out undesired harmonics. The output of the speed generator I9 is connected to oppose or buck the control voltage produced in the control unit 9. Thus, the speed generator I9 and the output of control unit 9 are connected in series opposition across the primary of transformer 19.. The

phase adjustor 91 is used to assure that the voltage output of speed generator I9 is exactly in phase opposition to the control voltage obtained from control unit 9. Accordingly, it is substantially the arithmetic difference between these two voltages which operates the motor I1.

The magnitude of the voltage input to amplier 83 needed to operate motor I1 at its full torque and speed is made very small compared to the voltage generated either by the speed generator or the control unit. The amplier 83 is advjusted to saturate at this small voltage; that is, any voltage greater than this predetermined small voltage is ineective to increase the amplifier output voltage, which remains at the motor full speed voltage. Of course, any amplifier input voltage smaller than the saturating voltage will yield an output voltage less than the motor full speed voltage. and the motor will rotate at less than full speed. As an illustrative example, the full-speed generator output, and the full deection control voltage, may be about 30 volts, while the amplifier saturating voltage may be about 0.3 volt.

In operation, starting from a standstill, the control handle II may be partially deflected, for example, to give a control voltage of 20 volts. Since at this instant the speed generator I 9 is at standstill, ithis control voltage is unopposed and is fully applied to the amplier. However, due to the saturation effect in amplifier 83, only 0.3 volt is effective, which applies full starting torque to the motor, which therefore immediately accelerates at maximum rate. `Acceleration will continue until the generator output differs from the control Voltage only by sumcient voltage dierence to maintain motor speed sufficient to yield that generator output. Since the voltage difference will be less than 0.3 volt, in the example used, it will be seen that the generator output voltage will be substantially equal to the control voltage, and, therefore, the motor speed. which provides the tracking velocity, is substantially proportional to the control voltage, and hence to the pressure (or deflection) applied to the control handle 35 II. Rheostat |03 is used to adjust the generator voltage to the proper value,

The function of 'prediction motor 21 is to position shaft 25 in accordance with certain prediction data. whereby the signals transmitted by synchro-transmitters 3 I, 33 will correspond to the position of the target at the future instant of impact by the projectile. The prediction data to be allowed for may include time of ight of the projectile, super-elevation, wind velocity, air density, etc.

The actual time of night t is determined by the range and altitude of the target. If the sight, and

therefore the gun, is tracking at an angular velocity w, then the angular lead necessary to compensate the gun for time of night t will be at. Since the speed generator I9 rotates at a speed proportional to the tracking speed, its output voltage will be proportional to u. In order to obtain a voltage proportional to wt, we use a potentiometer connected across the output of the speed generator. The full generator voltage is assumed to correspond to maximum time of night. This determines the proportionality factor between the voltage corresponding to the lead angle and the time of night. For-any other time of night, the tap |01 ofv potentiometer |05 is adjusted so that only a fraction of the vgenerator voltage, equal to the actual time of night divided by maximum time of night, is effective. In this way, a voltage proportional to wt is obtained and the proportionality is maintained both for varying angular velocities of sight I and for varying times with other prediction voltages, connected to terminals |09. which represent the other factors to becompensated for. These other prediction voltages may be obtained in any suitable manner. Of course, each of these other prediction voltages is made proportional to its required lead angle by the same proportionality factor as used for time of flight prediction. Hence, the total voltage represents, with a proportionality factor, the total lead angle necessary. Fig. 3 shows the means for positioning prediction motor 21 at this total lead angle in response to the prediction voltages.

Prediction motor 21 is mechanically coupled as by shaft 25 to prediction potentiometer 29. This potentiometer 29 is connected across transformer I I, which in turn is energized by current of line frequency from source 13.

A rate amplifier I I3, which may be of any well known type which yields an output voltage containing time derivative components of the input voltage, of the first and/or higher orders, as well as amplified input components, has one input terminal ||5 connected to terminal `I0!! of the prediction voltage input. The other terminal |09 is connected to one terminal |01 of the time of night potentiometer |05, whose other terminal |06 is connected by lead ||0 to the center tap I I9 of the secondary of transformer III. The other input terminal ||1 of rate amplifier ||3 ls connected to the movable arm I2| o'f the prediction potentiometer 29. .The output of the rate amplifier I I3 is connected to one winding |23 of two-phase prediction motor 21, whose other winding |25 is energized directly from the supply line 13. Rate amplifier ||3 may include any phase shifting circuits needed to insure phase quadrature between the voltages supplied to windings |23, |25 of motor 21.

When arm |2| of potentiometer 29 is at its center point |20, the voltage difference between points |20 and ||9 is zero, and the only voltage applied to the input IIS, ||1 of rate ampliner ||3 is the total prediction voltage. This voltage, operating through rate ampliner H3, will cause prediction motor 21 and potentiometer arm |2| to turn until the voltage between center point |20 and the new position of arm |2| of potentiometer 29 is equal and opposite to the prediction voltage, whereupon the input to ampliner I|9 becomes zero and the prediction motor stops. Since poof night. This voltage across the effective portion of potentiometer |05 is connected in series tentiometer 29 is wound linearly (that is, with constant resistance per unit length) the angle between point |20 and arm |2| will then be exactly proportional to the total prediction volta ze. This angle is also the angle through which shaft 25, and hence differential 2|, has turned. Accordingly, the prediction voltage is thus transformed into the required lead angle, and the position transmitted by synchro-transmitters 3|, 33 will be compensated for the required prediction data.

It is obvious that any change in-any of the prediction voltages will cause an immediate and corresponding change in the position of the prediction motor, so that the correct lead angle 1s always set intodinerential 2|.

Lead ||9 may be connected directly to center point |20 of prediction potentiometer 29. instead of to center point |I9 of transformer III, as shown in Fig. 3, without changing the operation of the device.

Fig. 4 shows an alternative control circuit for the device of Fig. l, using unidirectional control and prediction voltages instead of alternating voltages as in Fig. 3. The method of operation is quite similar.

Defiection of, or pressure on, control handle generates alternating control voltages in pick-up coils 61, 69. These voltages are rectified in fullwave rectifiers |21, |29 and are then connected in series opposing relation. The dotted arrows near coils 61, 69 indicate the relative polarities of the voltages induced in the coils 61, 69. In place of rectiiiers |21, |29, any phase-sensitive rectiner or demodulator may be used. The coils 61, 69 are connected in series opposition to form the input of such a demodulator. A suitable demodulator circuit is shown in Fig. 6.

The resultant direct voltage from the rectiners |21, |29 (or demodulator of Fig. 6) is applied to the input of D. C. amplifier I3I, wherein it is amplified. The output of D. C. amplifier |3| is connected in series bucking relationship to the output of speed generator I9', whose function and operation is the same as that of speed generator I9 in Fig. 3. However, generator I9' is a D. C. generator, either with a permanent magnet field or a field winding, energized by direct current, as will be described. Of course, the voltage ouput of generator I9 must be directly proportional to its speed.

The combined direct control and speed generator voltages are applied to modulator |35, which transforms the applied direct voltage into an alternating voltage of proportional amplitude, and of a phase corresponding to the polarity of the input. That is, the A. C. output voltage of modulator |35 reverses phase when the D. C. input voltage reverses polarity. Fig. 5 shows a suitable circuit which may be used as such a modulator. The operation of this circuit will be later explained. Y

The output of modulator |35 will be an alter` nating voltage whose phase corresponds to the direction of denection of control handle II and whose amplitude is proportional to the amplitude of the control handle denection. It will be understood that certain cases may require that this proportionality be not strictly observed. Any suitable relationship may be used. This output is fed into an'A. C. amplifier and phase shifter 0|, 83 similar to that in Fig. 3, whose output controls drive motor I1 as described above. 'Phase shifter 8| insures that the energization of field winding 85 of drive motor 1 is ln quadrature with that of field winding 81.

Incorporated in the input circuit of modulator |35 is the integrating circuit |31 for eecting velocity plus acceleration tracking control. This circuit comprises a potentiometer |39 connected across the speed generator output and having a movable arm |4| connected through a resistor |42 to the xed contact of a single-pole singlethrow switch |43. Connected across the two fixed contacts of a single-pole double-throw switch |45 is a condenser |41. One terminal of this condenser |41 is connected to a terminal of the speed generator |9, while the other terminal is connected to the movable contact of switch |43. l'he movable contact of switch |45 is connected to one output terminal of D. C. amplier |3| and also to a resistor |49 whose other side is connected to the input terminal |38 of modulator I 35. Resistor |49 is selected to have a high value of resistance, and to give a large time constant with condenser |41. A potentiometer |53 is connected across the output of D. C. amplifier 3|, and a switch can selectively connect the input terminal |35 of modulator |35 to either the movable arm |55 or the fixed terminal |56 of potentiometer |53. The three switches |5i, |43, |45 are mechanically ganged so as to be operated simultaneously.

In the switch position shown in Fig. 4, the circuit will operate with straight velocity tracking; that is. theV drive motor velocity will be proportional or will at least correspond to the control handle deflection, as described above. In this position, condenser |41 is charged through current limiting resistor |42 to a voltage somewhat less than the generator voltage, by means of the potentiometer |35. The time constant of the charging circuit |42, |41 is made small so that the condenser voltage will closely follow changes in generator voltage. The charging voltage depends on the position of arm |4| of potentiometer |33. i

When switches |43 and |45 are switched to their other positions, the voltage across condenser |41 is placed in opposition to the generator voltage, across resistor |49. The voltage across this resistor |49 will be the generator voltage less the condenser voltage. This difference voltage will be much less than the voltage across potentiometer |53, which at the Amoment of switching was substantially equal to the generator voltage. In order to prevent abrupt speed change of drive motor Il due to the excess of the voltage across potentiometer |53 over the voltage across resistor |49, switch |5| is actuated simultaneously with switches |43 and |45, and acts to reduce the effective voltage output of D. C. amplifier |3| to a value nearer the difference voltage.

Since the generator output voltage is greater than the charged condenser |41 voltage, the generator i9 will tend to further charge condenser |41, through resistor 49. The voltage drop across resistor |49 produced by this charging current must be substantially equal and opposite to the voltage across the effective part of potentiometer |53; otherwise, the drive motor |1 will speed up or slow down so as to make the drop across resistor |49 have a value equal to that across potentiometer |53. If control handle is held in constant deflected position,- a constant voltage will be developed across potentiometer |53. However, the voltage drop across resistor |49 will tend to decrease, since the charging current of condenser |41 will decrease as full charge is appreached. The only way in which the voltage drop across resistor |48 can be maintained equal to that across the effective part of potentiometer |53 is for the generator to continually increase velocity to maintain constant charging current. Hence control handle becomes an acceleration control in addition to a velocity control, as it is with the switches |43, |45, |5| in their voriginal position.

From another point of view, the generator voltage V must be equal to the sum of the voltage drop across resistor |49 and condenser |41. That 1s,

where R is the resistance of resistor |49, c is the capacitance of condenser |41 and i i's the current owing in the circuit. It is clear that V is proportional to the tracking speed s. Also, the drive motor circuit causes the drop across resistor |49 to be maintained practically equal to the control voltage, which is proportional to deflecton D of control handle Hence, iR is proportional to D, or i is proportional to D. Neglecting proportionality constants, the above equation may be transformed into This last equation shows that the tracking control has both a velocity and an acceleration component. That is, a constant deflection D will give a certain constant component of tracking velocity, as shown by the first term of the right side of the equation, and in addition will give a constantly increasing tracking velocity component due to the integrating eiect of the second term. Hence the control handle becomes both a velocity and an acceleration control.

If the control handle |I is released, so that zero voltage appears across potentiometer |53, the motor will drop its speed until the generator voltage output equals the condenser voltage. Thereafter the motor will travel at constant velocity; if the velocity should change, charging or discharging current from condenser |41 will flow through resistor |49, whose voltage drop will control the motor to restore its speed. 'I'he drive motor can be made to slow down only by reversing the deflection of the control handle, which therefore acts again as an acceleration control.

With zero control voltage, D becomes zero, so that the iirst term of the equation disappears, leaving only the integration term. Hence, S will be maintained constant at the value of the integrated term.

The importance of the combined velocity and acceleration control arises from the methods used in tracking. When an object is sighted, it is desirable to accelerate the sight to overtake the ob ject, and then keep it trained on the object. The present device permits such operation. Acceleration is provided by control handle deflection, whereby the object may be overtaken, then release of the handle will permit the sight to continue tracking at constant velocity.

A further advantage arises where the sight may be tracking by itself at the proper velocity, but behind the object. Then deflection of the control handle will apply enough additional tracking velocity, by the first term of the last equation, to enable the sight to overtake the object. Then release of the handle will permit the sight to resume practically the same tracking velocity as before, since the integration term of the equation source 13.

ll will be little affected by the brief period of increase'i velocity. v

Another useful method of operation is to use straight velocity tracking until the object is sighted. Then throwing the ganged switch of Fig. 4 to its other position will automatically continue the same tracking velocity, with the control handle at neutral.

Fig. 4 also shows a D. C. operated prediction control circuit which is quite similar to the prediction circuit of Fig. 3. The time-of-ight prediction voltage, which is proportional to the correction angle needed for time-oiflight correction, is derived as in Fig. 3 from time-of-ilight potentiometer |05 connected across the output of speed generator i9'. This voltage is now a direct voltage since the speed generator output is a direct voltage.

The other prediction voltages may be obtained from a transformer |51 whose primary |59 is energized directly lfrom the alternating supply Transformer |51 has plural similar secondary windings |6|, shown in this instance. for illustrative purposes only, as four in number. Each secondary winding |6| corresponds to one prediction quantity to be compensated for. It will be clear that as many secondary windings may be'used as desired.

Each secondary winding |5| is shunted by a centertapped resistor |63 oi' high resistance value, and by a potentiometer |65. The variable arm |61 of each potentiometer |65 is controlled in accordance with the value of the quantity for whichl prediction correction is required, in such fashion that .the voltage between each variable arm |61 and its corresponding centertap of resistor |63- is proportional, by the same proportionality factor, to the prediction angle needed for correction of that quantity. This may be accomplished by driving the arms of linear wound potentiometers |65 from the mechanism which computes the required prediction angles, through cams which yield the required relationship, or by using direct drive and non-linear wound potentiometers |65 which will also yield .the proper voltage-angle relationship. A suitable system is shown. in Bond Patent 2,208,623. Any other means for obtaining these prediction voltages maybe used.

These prediction voltages are added by being connected in series, as shown. lSince these voltages are derived from similar plural secondary windings of the sa me transformer, their phase relationships will all be phase coincidence or phase opposition, so that they may be added arithmetically to produce the required resultant prediction voltage. The resultant is applied to the input of full-wave demodulator |69 by means of transformer |1I. The circuit'of a suitable de modulator is shown in Fig. 6. The output of this demodulator |69 is a direct voltage whose amplitude corresponds to the amplitude of the input alternating voltage and whose polarity corresponds to the phase of the input voltage.

The output direct voltage from demodulator |69 is connected in series with the direct time-ofight prediction voltage, as in Fig. 3, to give the total prediction voltage.

.The prediction potentiometer 29 has a circuit exactly the same as in Fig. 3, except that D. C. energization is'used. The energizing potential for potentiometer 29 is obtained for alternating supply line 13 by means of full wave rectifier |13 having iilter choke |15 and filter condenser |11. Choke |15 may be' replaced by the ileld winding of speed generator |9' when an electromagnet field is used for that generator. In this way, since all the prediction circuit voltages are derived from the same source, namely, source 13, any iiuctuation in source voltage will have equal proportional effect on all voltages, so that the circuit as a whole is independent of source voltage uctuations. This arises from the fact that the balancing voltage from potentiometer 29 varies in the same way as the prediction voltages, upon any change in supply voltage.

As in Fig. 3, potentiometer 29 is rotated until .the voltage between its arm and its center point balances the total prediction voltage. This is done by connecting the total prediction voltage and the potentiometer voltage in opposition across the input ofdevice |19, which includes a D.C. ampliller, a modulator which converts reversible polarity D.C. into reversing phase A.C., and an A.C, amplifier. The modulator may be of the type shown in Fig. 5. Either or both the D.C. and A.C. amplifier may include rate circuits for insuring dead-beat and anti-hunting operation of prediction motor 21. Also, the A.C. circuits in device |19 may include proper phase shifting apparatus to cause the voltage output to be in quadrature with the voltage of line 13, to insure proper operation of .two-phase prediction motor 21. The operation oi this circuit is the same as that of Fig. 3. and positions shaft 25 at the angle corresponding to the total prediction voltage.

Fig. 5 shows a push-pull modulator circuit suitable for use in the circuits of Fig. 4 as the modulator |35. This modulator circuit converts a reversing polarity D.C. into a corresponding reversing phase A.C. The direct input voltage is applied to input terminals |90, |8| and is am plied in conventional D.C. amplifier |83, the amplified direct voltage appearing across centertapped resistor |85. This amplied voltage is applied in opposition to ythe two grids |81, |89 of a twin-triode tube |9| by means of a centertapped input resistor |93 whose center-tap |95 is connected to cathodes |91, |99 of twin-triade |9| by means of a. cathode bias resistor 20|. Grid current-limiting resistors 203 may be used to prevent excessive grid current, should any grid swing positive.

Anodes 205, 201 are connected to the outside terminals of center-tapped resistor 209 in parallel with one primary 2I| of output transformer 2|3. A source of alternating current 223 of line frequency is connected between the center taps and 2 I5 of resistors |93 and 209, respectively.

Let it be assumed that, for a particular polarity of input voltage, grid |81 is positive with respect to centertap |95 and grid |09 negative. Then, on positive half cycles of the applied A.C., anode 205 will have increased current, but anode 201 will have decreased current, compared to the current with zero input voltage to grids |01, |99. On negative half cycles neither anode will conduct. Hence, a voltage drop of a particular polarity appears across resistor 209, and only during positive half cycles of the supply voltage. This voltage drop will give a half-wave output from transformer 2|3 of one particular phase. If the input polarity were to reverse, making grid |89 positive with respect to point |95, and grid |81 negative, then, in the same way, anode 201 would have increased current, and anode 205 decreased current. and again only on positive half cycles of the applied A.C. This would cause a voltage drop to appear across resistor 209 of opposite polarity, giving an output half-wave from transformer 2| 3 of opposite phase from that of the rst instance described. Thus, the phase of the output voltage is sensitive to the polarity of the input voltage.

In order to provide a full-wave output, which minimizes distorting harmonics, an exactly similar twin-triode 2| 1 is used, with its input connected in parallel with the input to twin-triode |9I. The output of tube 2|1 is connected to a second primary 2|9 of transformer 2| 3 by a circuit identical to that of tube |9I. The cathodes of tubes |9| and 2|1 are connected together as by conductor 22|, and their anodes are energized from the same source. However, the anodes of tube |9| are energized in phase oppositionwith respect to the energization of the anodes of tube 2|1. This is accomplished by supplying both tubes from source 13 by means-of a transformer 225 having a center-tapped secondary. The center tap 221 is connected to the center-tap |95 of input resistor |93, and the outer terminal of one secondary section 223 is connected to the anodes of tube |9| by means of the center-tap 2|5 of resistor 269, while the outer terminal of theother section 229 is connected in similar fashion to the anodes of tube 2|1.

As a result of this connection, tube. |9| will conduct on half-cycles of the applied A.C, of one polarity, while tube 2|1 will conduct on the halfcycles of opposite polarity. As described above, the phase of the output voltage will reverse when the polarity of the input voltage reverses. 'I'he device of Fig. is therefore a full-wave modulator suitable for use with the circuit of Fig. 4.

Fig. 6 shows a full-wave demodulator suitable for use with the circuit of Fig. 4. The reversible phase A.C. input is applied to the primary winding of transformer 23| which has a center-tapped secondary winding having two sections 233, 235. 'I'he voltage across section 233 is applied cophasally to grid 231 of twin-triode 24| and to grid 245 of tube 241. The voltage across section 235 is applied cophasally to'grid 239 of tube 24| and to grid 243 of tube 241. Hence, the grids 231 and 239 of tube 24| are energized in phase opposition as are grids 243 and 245 of tube 241. Current limiting resistors 203 may be used. The cathodes of both tubes are connected together and to the center tap of the secondary winding of transformer 23|. Itv desired, a fixed bias voltage may be inserted between points 234 and 240, or cathode bias resistors may be used in the cathode circuits of the two tubes.

The anodes 249 and 25| of tube 24| are energized in phase opposition from the secondary winding of a transformer 265 fed from the A.C. source 13.. The center tap of this secondary winding is connected to the cathodes by load resistor 251, which is by-passed by lter con.. denser 259. Anodes 253, 255 of tube 241 are energized in similar fashion from transformer 261 and have a similarly connected load resistor 26| and lter condenser 263. Transformers 265 and 261 are so connected that anodes 2.49 and 255, Whose corresponding grids are cophasally energized, are energized in phase opposition. Also, anodes 25| and 253 are energized in phase opposition.

Across load resistors 251 and 26| connected in series, there is connected a filter circuit 269 for filtering out all A.-C. components, leaving only pure rectified D.C. at output terminals 21|, 213. This filter includes a choking transformer 215 having its terminal 21| and its secondary wind- 14 ing in series with terminal 213. Either primary or secondary winding, or both, may be tuned to the frequency of the predominating A.C. component, which is twice the line frequency, A further by-pass condenser 211 is also used.

The input voltage to transformer 23| is of the same frequency as source 13, and is adjusted by any suitable means to be cophasal (or anti-phasal) with the voltage oi source 13.

Let it be assumed that the phase of the input to transformer 23| is such that, at a particular instant of time to be considered, grids 231 and 24-5 are positive with respect to their cathodes, while grids 239 and 243 are negative. Furthermore, let it be supposed that at this same instant, anodes 249 and 253 are positive with respect to their cathodes, and anodes 25| and 255 are negative.

Then anode 249 will conduct, since both it and its grid are positive. Anode 25| will not conduct, being negative. Anode 253 will not conduct, its grid 243 being negative. Anode 255 will not con` duct, being negative. Accordingly, a voltage will appear only across resistor 251, making output terminal 21| negative with respect to terminal 213.

In the succeeding half-cycle from the instant of time considered above, grids 231 and 245 will be negative, grids 239 and 243 will be positive, anodes 249 and 253 will be negative and anodes 25| and 255 will be positive. Hence, only anode 25| will conduct, the remaining anodes and/or grids being negative. Again current will be passed through resistor 251, and the same polarity of D.C. output will be obtained.

If the input to transformer 23| should reverse phase, with respect to source 13, then, at one instant of time grids 231 and 245 would be negative, grids 239'and 243 would be positive, anodes 249 and 253 would be positive and anodes 25| and 255 would be negative. Under these conditions only anode 253 would conduct, yielding a D.C. output of opposite polarity from that of the case considered above.

On the succeeding half-cycle, all polarities would reverse, and only anode 255 would conduct.

Accordingly, Fig. 6 gives a phase-sensitive, fullwave rectier or demodulator, suitable for use in two separate single tubes could equally well be used. Also, tubes |83, |9I, 2I1, 24| and 241 need not be of the triode type, as shown, but may be of any type of amplifier tube incorporating a control grid.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described our invention, what we claim and desire to secure by Letters Patent is:

- 1. A target tracking device comprising a sight, motive means for rotating said sight, generating means driven by said motive means for generating a unidirectional voltage dependent on the speed of rotation of said sight, control means for generating. a. unidirectional signal voltage corresponding to a desired speed of rotation of said sight, and means for controlling the speed of rol tation of said motive means by the arithmetic diiIerence of said voltages, whereby said sight will rotate at said desired speed.

2. A target tracking device as in claim 1, further comprising means for transmitting the orientation of said sight to a remote point, means connected to the output of said generator means for obtaining a prediction voltage corresponding to a desired angular correction of the orientation of said sight, and means under the control of said prediction voltage for compensating said orientation transmitting means for said angular correction.

3. A target tracking device comprising a sight, motive means for rotating said sight, generating means driven by said motive means for generating a speed voltage dependent upon the speed of rotation of said sight, control means for generating a signal voltage corresponding to a desired speed of rotation of said sight, means for obtaining a voltage corresponding to said speed voltage, and means for controlling the speed of rotation of said motive means by the algebraic sum of said signal voltage and the difference between said speed voltage and said obtained voltage whereby said Ymotive means will continue to operate without signal voltage at a speed corresponding to said obtained voltage.

4. A target tracking device comprising a sight, motive means for rotating said sight, generating means driven by said motive means for generating a voltage dependent upon the speed of rotation of said sight, control means for generating a signal voltage corresponding to a desired speed of rotation of said sight, means for controlling the speed of rotation of said motive means by the arithmetic difference of said voltages, means for transmitting orientation of said sight to a remote point, means connected to the output of said generating means for obtaining a prediction voltage corresponding to a desired angular correction of the orientation of said sight, and means under the control of said prediction voltage for compensating said orientation transmitting means fory said angular correction.

5. A target tracking device as in claim 3, in which said control means comprises a control handle mounted in cantilever fashion for deflection about a single point, a magnetic armature carried by said handle. two parallel magnetic paths bridged at one end by a magnetic member and at the other end by said armature, means for applying equal alternating magnetomotive forces to said two paths. a coil linking each path, whereby the voltage induced in each coil will depend upon the position of said armature, and means for connecting said coils in series opposition, whereby the voltage across both said seriesconnected coils will reverse phase as the armature passes through theposition yielding` 'equal coil voltages. l

6. A control unit comprising a casing, a control handle fixed at one end within said casing for cantilever deilection with respect to said casing, four pickup coils having their axesv parallel to the neutral undeected axis of said handle and mounted equidstant from said neutral axis both radially and angularly, an energizing coil mounted coaxial with said neutral axis, open magnetic circuit means connecting said pickup coils with said energizing coil, a magnetic armature carried by said handle and positioned to complete said magnetic circuits, means for energizing said energizing coil from a 'source of alternating current, whereby voltages will be in- 7. A control unit comprising-a support, a can- I tilever carried by said support, a control handle arranged on vsaid cantilever for displacement in any transverse direction relative to said support, the amount of displacement of said handle thereby being dependent upon the magnitude of pressure applied thereto, and means respon.

sive to displacement of said handle for producing control voltages corresponding to the direction and magnitude of the pressure applied to said handle.

8. A control unit as in claim 7, wherein said voltage-producing means comprises a plurality of magnetic poles xed with respect to said casing and carrying coils energized by alternating current, and a magnetic armature member ilxed to said control handle for motion therewith.

9. A target tracking device comprising a sight, motive means for moving said sight, a control handle mounted for deflection about a single point, means responsive to deflection of said handle for moving said sight in a direction corresponding to the direction of deection of said handle and at a speed corresponding to the magnitude of deflection of said handle, means for transmitting the instantaneous orientation of said sight to a remote point to control the orientation of a remotely situated gun, means to compensate the transmitted orientation for prediction data whereby the gun will be oriented toward the future position of the target, and means for causing the sight to continue tracking at substantially constant speed without deection of said handle.

10. A target tracking device comprising a sight, motive means for moving said sight in azimuth, motive means for moving said sight in elevation, a control handle mounted for deilection in all transverse directions about a ilxed point, means for controlling the velocity of said first motive means in response to the component of deflection of said control handle in a predetermined direction, means for controlling the velocity of said second motive means in response to the component of deiiection oi' said control handle in a different predetermined direction, and means responsive to the speed of each of said motive means for supplying signals to said control means for operating said motive means in response to an integrated value. of its corresponding component of handle deflection.

l1. A target tracking device comprising a sight. motive means for orienting said sight, a control handle mounted for deflection, means for producing a control voltage in response to deflection of said handle, means for integrating said voltage over a period of time, and means for controlling said motive means both by said integrated voltage and by said control voltage.

12. A target tracking device comprising a sight. a control handle, a cantilever securing said handle on said sight permitting relative displacement in any transverse direction, the amount o! disi7 placement being dependent upon the magnitude of pressure applied thereto, and means responsive to pressure applied to said handle for moving said sight in a direction corresponding to the direction of said pressure and at a velocity corresponding to the magnitude of said pressure.

13. A control unit comprising a casing, a eontrol handle mounted in cantilever fashion with respect to said casing for deection in any radial direction with respect to the axis of its undeflected position, a stabilizing reference surface rigidly mounted on said casing and adjacent to said handle ina position yto be used by an operator as a reference with respect to which said handle may be deflected, said surface and said handle being formed to conform to the contour of the hand of the operator whereby precise and steady neection of said handle may be obtained, and means responsive to arbitrary deflection of said handle for producing voltages each corresponding in polarity and magnitude to the sense and magnitude of a component of said deection in a predetermined direction.

14. A control system for a movable object comprising motive means for moving said object, generating means for generating a speed signal dependent upon the speed of said object, control means for producing a control signal, and means for controlling the speed of said motive means according to the diierence between said control signal and the time derivative of said speed signal.

15. A control system for a movable object comprising motive means for i moving said object,

generating means for generating a speed signal dependent upon the speed of said object, a differentiatingnetwork connected to said generating means for obtaining the time derivative thereof, control means for producing a control signal, and means connected to said differentiating network and said control means for controlling the speed of said motive means according to the difference between said control signal and said time derivative signal.

16. A control system for a movable object comprising a motor for moving said object, a generator driven by said motor for generating a speed signal dependent upon the speed of said object, a condenser and resistance network connected to said generator for differentiating said speed signal, a control device for producing a control signal, and means for controlling the speed of said motor according to the difference between said control signal and said differentiated signal 17. A target tracking device comprising a sight, motive means for rotating said sight, generating means driven by said'motive means for generating a voltage dependent upon the speed of rotation of said sight, control means for generating a signal voltage corresponding to a desired speed of rotation of said sight, means for controlling the speed of rotation of said motive means by the arithmetic difference between said voltages, means for transmitting the orientation of said sight toa remote point, means connected to said generating means for obtaining a prediction voltage corresponding to a desired correction of the orientation of said sight, and means controlled by said prediction voltage for oisetting said orientation transmitting means relative to said sight in accordance with said correction whereby the desired corrected orientation is transmitted by said transmitting means.

18. A control system for a movable object comprising motive means for moving said object, generating means operated by said motive means for generating a iirst speed signal dependent upon the speed of said object, means connected to said generating means for producing a second speed signal opposing said rst speed signal, control means for producing a control signal, and means for controlling the speed of said motive means according to the algebraic sum of said control signal and the difference between said speed signals.

19. A control system for a movable object comprising motive means for moving said object, generating means operated by said motive means for generating a rst speed signal dependent upon the speed of Ysaid object, means connected to said generating means for producing a second speed signal opposing said rst speed signal, a combining circuit connected to said generating means and said last-named means for combining said speed signals in opposition, control means for producing a control signal, and means connected to said combining circuit and said control means for controlling the speed of said motive means.

20. A control system for a movable object comprising motive means for moving said object, generating means operated by said motive means for generating a rst speed signal dependent upon the speed of said object, a condenser connected to said generating means for producing a second speed signal in opposition to the signal from said generating means, control means for producing a control signal, and means for controlling the speed 0f said motive means according to the algebraic sum of said control signal and the dinerence between said speed signals. a

21. A control system for a movable object comprising a motor fdr moving said object. a generator driven by said motor for producing a rst speed signal dependent upon the speed of said object, a condenser connected in series with said generator, an impedance connected in parallel with said series circuit. control means for producing a control voltage, and means for controlling the speed of said motor according to the algebraic sum of said control voltage andthe voltage across said impedance.

22. Tracking apparatus comprising a sight, a motor for turning said sight, a generator driven by said motor for producing a rst speed voltage dependent upon the speed of said sight, means connected to said generator for producing a second speed voltage in opposition to said first speed voltage, control means for producing a control voltage, and means for controlling the speed of said motor according to the algebraic sum of said control voltage and the difference between said speed voltages.

23. A tracking control comprising a controller and a driven object, motive means for rotating the latter. a generator driven by said means producing a voltage proportional to the rotary speed of said object, means at the controller producing a voltage proportional to a desired speed of said object, other means deriving a voltage corresponding to said generator voltage, and means for opposing said generator voltage by said derived voltage whereby said motive means will maintain its speed for a time without a controller voltage.

HARVARD L. HULL. WILLIAM C. HARTMAN. RAYMOND C. GOERTZ. 

